Extraction

ABSTRACT

A method of, and apparatus for, extracting a soluble component of a soluble material, in which the material is introduced into a press and subjected to pressure and while that pressure is maintained on the material, a liquid solvent for the component is introduced into the press so as to pass through the material. In one variant of the invention the pressure on the material is increased after the liquid solvent has been added and in another variant the liquid solvent introduced into the press itself contains dissolved elements of the soluble component.

United States Patent [72] Inventors James Shann Hull; David VincentBeasant, South Cave, both of England [21] Appl. No. 806,909

[22] Filed Mar. 13, 1969 [45] Patented Sept. 21, 1971 [73] AssigneeRose, Downs & Thompson 'rnited Kingston-upon-l-lull, Yorkshire, England[32] Priority May 7, 1968, Aug. 2, 1968 [33] Great Britain [31 21526/68and 36942/68 [54] EXTRACTION 5 Claims, 5 Drawing Figs.

[52] [1.8. CI 127/7, 23/270, 100/74, 127/6, 127/43, 127/44 [51] Int. Cl.C13d1/12, C13d1/10,C13d 1/04 [50] Field of Search 127/2-8,

[56] References Cited UNITED STATES PATENTS 1,015,371 1/1912 Wolfe100/72 1,3 46,594 7/1920 Deerr 100/75 2,063,367 12/1936 De La Roza...100/73 X 3,005,398 l0/l96l Sandler 23/270 X 3,037,445 6/1962 Burner etal. 100/72 X 3,111,080 11/1963 French etal 100/73 X 3,181,454 5/1965Ginaven et al 100/74 Primary ExaminerMorris 0. Walk AssistantExaminer-D. G. Conlin Attorney-Holcombe, Wetherill & Brisebois ABSTRACT:A method of, and apparatus for. extracting a soluble component of asoluble material, in which the material is introduced into a press andsubjected to pressure and while that pressure is maintained on thematerial, a liquid solvent for the component is introduced into thepress so as to pass through the material. In one variant of theinvention the pressure on the material is increased aft-er the liquidsolvent has been added and in another variant the liquid solventintroduced into the press itself contains dissolved elements of thesoluble component.

" PATENTE'U sEP21 1911 3,607; 391

SHEET 1 UP 2 l l l I 'l FIG. 4

INVENTOR ATTORNEY PATENTEU SEPZI I97! 350?, 391

SHEET 2 BF 2 INVENTOR ATTORNEY EXTRACTION This invention relates to theextraction of soluble components from solid materials and isparticularly, but not exclusively, concerned with the extraction ofsugar from sugarbearing materials, such as sugar cane and derivatives ofsugar cane.

At present it is customary to pass sugar cane, possibly after theremoval of the external fibers, through grinding rolls in order torupture the sugar-containing cells and to extract part of the water anddissolved sugar. The remaining sugar is then removed by further rollingwith the addition of water or weak sugar solution to the crushed canebetween each rolling. The remaining sugar may also be removed from thecrushed cane by treatment in a diffuser. It has been suggested that thecane should be treated in a series of screw presses and mixers, waterbeing added to the cane material between successive pressings, i.e.while the material is subject to zero compression. It has also beenproposed to inject water into a screw press at an intermediate pointalong the barrel, but, in that proposal, the press was speciallydesigned by the provision of an expansion chamber to ensure that thepressure on the material was relieved at the point the water wasinjected.

The present invention is based on our discovery that, contrary toexpectations, a higher extraction of soluble components from solidmaterials is achieved if the pressure on the material is maintainedwhile the liquid solvent for the component is injected, than if thepressure is relieved.

In the case of sugar extraction, it has been found possible to achieve a99 percent sugar extraction rate by pressing under increasing pressureand injecting water into the cane under pressure before each pressureincrease.

One aspect of the present invention resides in a method of extracting asoluble component of a solid material, in which the material issubjected to pressure and, while that pressure is maintained on thematerial, a liquid solvent for the component is passed through thematerial. Preferably the pressure on the material is increased further,after the liquid solvent is added. The pressure may be progressivelyincreased, and the liquid solvent applied to the material twice or moretimes at different intermediate pressure on the material. If desired theliquid solvent introduced into the material for extraction of thesoluble component may itself contain dissolved elements of thatcomponent. Thus, the liquid solvent may be partly or wholly constitutedby the liquid previously passed through the material.

A second aspect of the invention resides in a process for extractingsugar from sugar-bearing material in which the material is introducedinto a press adapted to permit escape of liquid pressed from thematerial, and subjected to progressively increasing compression, and inwhich a sugar solvent is injected into the material in the press on atleast two occasions during the increase in pressure and withoutrelaxation of the pressure. The sugar solvent may be either water or apart of the pressed miscella which is recirculated back and mixed withthe water feed.

A third aspect of the invention resides in an apparatus for extracting asoluble component of a solid material, including a press adapted topermit escape of the component pressed from the material, means forintroducing the material to the press, means for injecting a liquidsolvent for the component into the interior of the press is that thepressure on the material is maintained and means for collecting thecomponent pressed from the material.

The invention will be more readily understood by way ofexample from thefollowing description of methods of extracting sugar from sugar cane,reference being made to the accompanying drawings, in which:

FIG. 11 illustrates diagrammatically a first method of treating sugarcane in a screw press,

FIG. 2 illustrates diagrammatically a second method,

FIG. 3 is an end view of part of the cage of the screw press of FIG. 1or FIG. 2,

FIG. 4 is a side view of a liner bar, and FIG. 5 is a section on theline V-V ofFIG. 4.

The screw press indicated generally at il2 in FIG. I and FIG. 2 is amodified form of a known press used for pressing liquid from aliquid-bearing material. The known press comprises a screw rotating in aperforated cylindrical cage, the cross-sectional area between the screwand the cage reducing along the screw axis so that, as the material tobe pressed is carried along the screw, it is progressively compressedand the con tained liquid is forced through the cage perforations. Thecage is made up of a number of longitudinal sections, each made up of aseries of axially extending lining bars arranged in the form of acylinder and with spacers interposed between successive bars at theirends to form line perforations for the escape of liquid.

The press 12 shown in FIG. 1 has a cage formed in three sections, 13, M,15, the diameter of each of which is less than that of the previoussection, to obtain in steps the reduction in cross-sectional areabetween cage and screw. Defibered sugar cane is fed into the right-handend of the press as viewed in FIG. 1, via a feed hopper, and the pressedcane is removed from the left-hand end.

While the sugar cane is within the press 12 and while it is subject tothe high pressure developed within the press, it is washed with waterwhich is introduced into the press at high pressure, which acts as asolvent for the contained sugar, and which leaves the press through thecage perforations. Thus, in FIG. 1, high-pressure water on line 16 isfed to the feed hopper and to points of the three sections 13, 14, 15 ofthe cage, through the lines 17, l8, l9 and 20 respectively. Each oflines 17-20 has its own flow control valve 21 and flow and pressureindicators 22, 23 respectively, to enable the water to be supplied at apressure appropriate to the delivery location.

In order to obtain the injection of the water into the sections 13, M,15, special liner bars 24 as shown. in FIGS. 4 and 5 are employed. Eachsuch bar 24 has welded to its external surface a tubular socket 26, thecentral passage 27 of which is aligned with a passage 28 through the bar2d.

One segment 30 of the discharge half of each cage section 13, 14, 15 ismodified by the removal of the spacers between the liner bars and by thereplacement of one of those bars by an injector bar as shown in FIG. dand 5, the appropriate line 18, 19 or 20 being connected to the socket26 of the appropriate injector bar. FIG. 3 shows part of the modifiedsegment, the lining bars 31 being located hard up against one another,without the interpolation of spacers, and being held in place by wedgingstrips 32 between the end lining bar 31 and the shoe frame bar 33 onwhich the lining bars are mounted. The absence of cage perforationsadjacent the water injection ensures that the water penetrates the sugarcane within the press and does not emerge: until it has passed throughthe cane.

If desired the water supplied on line 1'6 may be replaced in whole or inpart by miscella, or sugar'rich water obtained from a previousextraction.

FIG. 2 illustrates an alternative form of extraction process using ascrew press, where the water is circulated a number of times through thesugar cane, increasing in sugar extraction each time. As in FIG. 1, thedefibered sugar cane is introduced into the right-hand end of the pressof FIG. I, the extracted cane being discharged at the left-hand end.

Water is supplied through line 35 and is raised by a high pressure pumpdiagrammatically indicated at 36 to a pressure in excess of thatobtaining within the press at the discharge end. The high pressure wateris then injected into the cage adjacent the discharge end through line37 and an injector lining bar as in FIGS. 4 and 5. After passing throughthe cane, the liquid leaves through the cage perforations and iscollected in a first tank 38 as weak miscella containing a smallproportion of dissolved sugar. From tank 38, the miscella is pumped by amedium pressure pump 40 through line M to an injection point locatedcentrally of the press. The liquid passes through the cane at that partof the press and is collected in a second tank d2. Finally the miscellain tank 42 is pumped by the lowpressure pump 43 through line to aninjection point at the input section of the press, and after passingagain through the sugar-rich cane is collected in a third tank 45 fromwhich it is discharged through line 46. The final concentrated sugarsolution is then treated for sugar recovery.

In place of the screw presses previously described, a hydraulic rampress may be used having a perforated cage and a water passage throughthe ram to the interior of the press. The press is filled with the caneand the latter compressed to a first high pressure of, say, 300lb/sq.in., sugar-rich moisture being expelled through the cageperforations. Without relaxing the pressure, water is injected into thematerial via the ram passage at a pressure sufficient to cause the waterto pass through the material, say, 100 lb/sq.in The press pressure isthen raised to say, 650 lb/sq.in., and a further quantity of waterinjected. Finally the press pressure is raised again to say, 800lb/sq.in. Operating with the press and water pressures given, a sugarextraction rate of over 99 percent can be obtained and no subsequentdiffusion treatment is needed. At the same time the moisture content ofthe extracted material is reduced to under 55 percent.

Efficient extraction can be obtained by using a single injection ofwater and without increasing the pressure afterwards. In this case, thehigher the press pressure at which water injection, the better theextraction rate. In place of water, miscella from a pervious extractionmay be used.

While reference has been made to the extraction of sugar from sugarcane, the process may be applied to increase the extraction rate inother solvent extractions, where the solvent may be other than water. Anexample is removal of oil from oil-rich vegetable matter.

We claim:

1. A process for extracting a soluble component of a solid materialcomprising the steps of subjecting said material to pressure to expelliquid from said material,

applying to said material in a first application fresh liquid solventfor said component while said material is subject to pressure, saidsolvent passing through said material and dissolving and removing someof said component,

collecting liquid solvent from said first application after havingpassed through said material,

applying, in a second application, some at least of said collectedliquid solvent to said material so as to pass through said material, and

maintaining pressure of said material between said solvent applications.

2. A process according to claim 1 in which the material is fed along aprescribed path and is subjected to increasing pressure,

said first and second solvent applications are made at points spacedalong said path,

fresh solvent is applied in the more downstream point along said path,and

at the more upstream point, the solvent applied is formed from liquidpressed from the material at the more downstream point.

3. Apparatus for extracting a soluble component from a solid material,comprising a screw press having a perforated cage and a screw mountedfor rotation in said cage to feed material along the press whilesubjecting said material to an increasing pressure,

means for introducing said material to said press,

injection means for injecting liquid into said press at two points atleast along its length, the pressure on the material being at leastmaintained between said points,

means for applying solvent for the component to each of said injectionmeans at a pressure such that said solvent passes through said material,

a series of tanks for separately collecting liquid pressed from thematerial adjacent each of said points, and

means for applying liquid from each tank, except the first,

to an injection means upstream of that tank.

4. Apparatus as claimed in claim 3 in which there are means forsupplying fresh solvent to the most downstream injection means. 5.Apparatus as claimed in claim 3 in which each said applying means is apump arranged in the fluid path between each tank and injector.

2. A process according to claim 1 in which the material is fed along aprescribed path and is subjected to increasing pressure, said first andsecond solvent applications are made at points spaced along said path,fresh solvent is applied in the more downstream point along said path,and at the more upstream point, the solvent applied is formed fromliquid pressed from the material at the more downstream point. 3.Apparatus for extracting a soluble component from a solid material,comprising a screw press having a perforated cage and a screw mountedfor rotation in said cage to feed material along the press whilesubjecting said material to an increasing pressure, means forintroducing said material to said press, injection means for injectingliquid into said press at two points at least along its length, thepressure on the material being at least maintained between said points,means for applying solvent for the component to each of said injectionmeans at a pressure such that said solvent passes through said material,a series of tanks for separately collecting liquid pressed from thematerial adjacent each of said points, and means for applying liquidfrom each tank, except the first, to an injection means upstream of thattank.
 4. Apparatus as claimed in claim 3 in which there are means forsupplying fresh solvent to the most downstream injection means. 5.Apparatus as claimed in claim 3 in which each said applying means is apump arranged in the fluid path between each tank and injector.